Field of the Invention
The present invention relates to a compressor.
Description of the Related Art
Conventionally, a screw compressor including a pair of screw rotors has been known. For example, Japanese Examined Utility Model Application Publication No. Sho 62-18390 discloses a compressor including a pair of screw rotors that have rotor shafts, a rolling bearing that receives the rotor shaft, a piston that supports the rolling bearing, and a working fluid supply flow passage that supplies a working fluid for pressing the piston toward the rolling bearing. The rolling bearing is in contact with the piston in an axial direction of the rotor shaft. In other words, the rolling bearing receives a load (radial load) in a radial direction acting on the rotor shaft as well as a load (thrust load) acting in the axial direction of the rotor shaft. The piston is in a shape of partitioning a rotor chamber which stores the rotor shafts and the rolling bearings and a cylinder chamber to which the working fluid is supplied from each other. The working fluid presses the piston so that a thrust load acting on the rolling bearing and an inverse thrust load act via the rolling bearing on the rotor shaft.
By the way, as the rotational speed increases, a quantity of oil stirred by a piston arranged in an oil bath increases, resulting in an increase in mechanical loss in a compressor having a balance piston structure. Moreover, it is difficult to extend the service life of the compressor by such a structure that the rotor shaft is supported by the rolling bearing as described in Japanese Examined Utility Model Application Publication No. Sho 62-18390.